Eia422a Interface Circuit Test Method
Original Publication Date: 1988-Mar-01
Included in the Prior Art Database: 2005-Feb-14
Described herein is a test method for an EIA422 interface circuit. It includes to check Exclusive-ORed result of two receive data to detect any failure in the send or receive lines. As shown in the figure, "+SEND" and "-SEND" lines from a driver 10 are respectively connected to "+RECEIVE" and "-RECEIVE" lines to a receiver 11 for a conventional wrap test. But, the wrap test is not adequate to detect failure in only one of these lines. In order to detect such a failure, a unique logic circuit 12 is provided. The logic circuit includes comparators 13 and 14 having positive inputs connected to the "+RECEIVE" and "-RECEIVE" lines, respectively, and negative inputs commonly connected to a voltage divider 15.